Light-emitting diodes are among the most efficient light sources currently available. Active efforts are made to develop white light emitting devices by combining blue LED with phosphors. For example, JP-A 2007-150331 discloses a wavelength converting member including garnet or the like, specifically a light-transmissive, homogeneous wavelength converting member capable of wavelength converting light emitted by a light emitting component, and a light emitting device including the wavelength converting member. The wavelength converting member is expected to have higher heat resistance and higher mechanical strength than the prior art wavelength converting layer including a phosphor and a resin in which the phosphor is dispersed, and is also expected to have high durability against the heat that increases as the output of light emitting components increases.
In the case of a wavelength converting member using garnet which is light-transmissive and homogeneous, a portion of light from a light source that is transmitted by the wavelength converting member travels straightforward through the wavelength converting member whereas a portion of light that is absorbed and wavelength converted by the wavelength converting member travels isotropically in all directions. Thus the transmitted light and the wavelength converted light have different patterns of light distribution. As a result, the light output from a light emitting device including such a wavelength converting member fails in color uniformity and only an illuminated surface with variations in color is available from the light emitting device. As the countermeasure to this problem, an opaque or translucent light-diffusing member is disposed outside the light emitting device to mitigate the visible variation in color of the illuminated surface. The use of the light-diffusing member leads to a lowering of light utilization efficiency because of a partial loss of light across the light-diffusing member.